It is well known that among the many substitutes which have been proposed to reduce the need and/or craving to smoke, chewing gums including nicotine have been found to be quite successful. In fact, it has been established that assimilation of nicotine from a source other than tobacco can be of considerable help to a smoker who wishes to give up smoking.
In order to have the desired effect, prior art chewing gums of the type in question had to contain from 1 to 4 mg of nicotine per 3 g strip of gum. Furthermore, the prior art chewing gums had to retain the nicotine so as to release the nicotine slowly over not less than 10 minutes during chewing. This slow release was necessary because a more rapid assimilation of the required amount of nicotine could give rise to undesirable side-effects such as, for example, heart palpitations, tachycardia, migraine, irritation of the mouth or throat, etc. The lower limit of 1 mg of nicotine was established, also according to the prior art, because no medium was known which could usefully be incorporated in a chewing gum and could release such a small quantity of nicotine over a period as long as 10 minutes.
A chewing gum which satisfies the requirements of the prior art is described in Italian Patent No. 1,044,563 corresponding to U.S. Pat. No. 3,901,248.
This patent describes the preparation of chewing gum including a cation-exchange resin which is finely dispersed in the gum base and to which predetermined quantities of from 1 to 5 mg of nicotine are bound. Although, on the one hand, such a chewing gum achieves the predetermined object of slowly releasing the nicotine, on the other hand, this chewing gum disadvantageously is organoleptically less pleasant precisely because of the presence of the cation exchange resin. Namely, the cation-exchange resin gives the gum a particularly unpleasant taste.
Italian Patent No. 1,045,528 corresponding to U.S. Pat. No. 3,877,468 describes a chewing gum including not less than 40% by weight of a gum base in which the nicotine is dispersed in the form of a free base or a pharmacologically-acceptable addition salt of nicotine, or even as a complex including an adsorbent substance which binds nicotine or a salt thereof. In this case, the chewing gum also has the desired advantage that it releases the nicotine slowly but, because of the high percentage of its gum base content, it has the disadvantage that it does not afford soft or linear chewing. The term linear chewing is intended to define a characteristic of the consistency of the chewing gum as a result of which the effort required to chew the same is constant or almost constant over a period of time. It is well known that a gum base is generally a fairly stiff, solid substance which must be used in quite small percentages, generally not greater than 25% of the finished product by weight, so that it can be softened or plasticized by the sugary matrix and, in particular, by the flavoring ingredients of the chewing gum.
The otherwise recognized effectiveness of the nicotine gums of the prior art may be frustrated by their mainly organoleptic disadvantages which often constitute a psychological alibi or justification for the smoker's lack of will to persevere in his attempt to give up smoking.